The use of fine-grain dating for samples such as pottery, loess, burnt flint and lacustrine sediments, and coarse-grain dating of aeolian, fluvial and glacial sediments is regularly undertaken.

While thermoluminescence (TL, the generation of a luminescence signal generated by thermal stimulation) is still conducted on pottery and burnt flint samples, the bulk of luminescence dating now uses optical stimulation as this releases a signal that is far more readily zeroed than that re-set by heat.

Free electrons, excited mainly by environmental alpha, beta and gamma radiation, become trapped within the crystalline defects of minerals such as quartz and feldspar, and continue to accumulate until exposure to daylight or sufficient heat evicts them, bleaching the sample of its signal, and effectively resetting the ‘luminescence clock’ to zero.The use of longer wavelength stimulation light to that of the emissions helps to ensure reliable evaluations and blue or green light is now most widely used for the stimulation of quartz.As feldspar can be measured using the longer wavelengths of infrared (IR) stimulation, a broader range of emissions are available for measurement (see Figure 4).Despite this, through the careful choice and collection of samples, as well as stringent preparation and analytical methods, it is possible to produce ages with an accuracy of between 5 and 12%.The dating of sediments using the luminescence signal generated by optical stimulation (OSL) offers an independent dating tool, and is used most often on the commonly occurring minerals of quartz and feldspar and, as such, has proved particularly useful in situations devoid of the organic component used in radiocarbon dating.